Electronic – Does the input polarity matter for a 12V DC adapter

adapterdcpolarity

I bought a car cigarette DC adapter yesterday with the following specs:

Input:  DC 12V
Output: DC 17V 

I'm planning to connect it to a 12V battery I have at home, but I was wondering if the adapter input polarity matter or could damage the adapter if reversed?

Best Answer

The adapter might have some sort of protection inside, but it will not work (and possibly it will fry) if you reverse the polarity. I bet you have this kind of plug:

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The tip is the positive contact while the side plates should be connected to the negative pole of the battery.

For extra safety, and since you are working with a somewhat big battery, add a fuse in series with your adapter: if you mess something up the fuse blows and the wires don't catch fire. The fuse should be rated a bit above the maximum input current that should be written somewhere on your adapter. Please note that it's well possible that there already is a fuse and that it's inside the above plug.